Numerical study of bund overtopping phenomena after a catastrophic tank failure using the axisymmetric approach

Hazardous materials are stored in the large tanks in the industry, e.g., a single LNG tank can be as large as 230,000 m³. Therefore, a catastrophic tank failure can cause a disastrous incident. A secondary containment, such as a bund, is required by regulations to control the risk; however, the released liquid may overtop from the bund due to its high kinetic energy converted from potential energy. Computational Fluid Dynamic (CFD) is a proper tool for the bund overtopping study, but there has been significant discrepancy among previous CFD studies. This work developed 2D CFD models of bund overtopping using the axisymmetric approach. A screening study on several turbulence models was performed, and RNG k-ε Standard Wall Functions (RNG k-ε SWF1) and Large Eddy Simulation WALE (LES WALE) were selected for a detailed comparison in terms of overtopping fraction and flow dynamic behaviour. Both RNG k-ε and LES models were systematically validated against experimental data, and the results indicate that LES model is slightly better than RNG k-ε model, and both models are acceptable based on the criteria of statistical performance measures.